[TUHS] PDP-8 (was: 2.11BSD cross compiler)

Greg 'groggy' Lehey grog at lemis.com
Thu Sep 30 14:22:29 AEST 2010

On Tuesday, 28 September 2010 at 22:59:22 -0400, John Cowan wrote:
> On Tue, Sep 28, 2010 at 10:38 PM, Larry McVoy <lm at bitmover.com> wrote:
>> Color me old school.  I like MIPS, I worked at SGI (got married to
>> an old school MIPS gal) but PDP-11 is so frigging intuitive.  How
>> can you not understand that instruction set?  If you can't, well,
>> sorry, not so much in my book.  It's like a stripped down C.
> Yeah.  I used it on and off, but my serious assembler programming
> was on the PDP-8.  Now *that* was seriously small, but you had to
> know the tricks, like how to find out the absolute address of the
> 128-word memory page following the one you are on when writing PIC
> code for OS/8 device drivers, or how to microprogram the operate
> instructions get interesting constants into the AC.

That was my first machine too (well, a PDP-12, which was really a
hybrid PDP-8/LINC-8, but I only used the PDP-8 instructions).  That
was a nice, compact instruction set.  It has the great advantage that
I can still remember just about every instruction today.  Remember the
autoincrement registers?  Even in those days they looked like a
kludge, but they helped a lot.

>> Come on - has anyone ever seen a better instruction set?  More
>> complicated, yeah, holy moly, yeah.  But cleaner?  We owe DEC
>> for that one.
> I remember how appalled I was when I saw the VAX instruction set.
> Luckily, it didn't matter: I never did assembler again.  Still,
> trying to make people think in octal at this late date seems
> unnecessary.

It's funny how long octal clung on.  It should have gone away with 8
bit bytes.  But somehow I still have a soft spot for octal, and
numbers like 7778 still look wrong.

>> Personally, I like anyone who can do any assembler.  One of my interview
>> questions is "have you written swtch?"
>>  If you don't get the question you are not an OS person,
>> if you are, of course you get it.

Hmm.  Am I expected to understand this?  Seriously, I don't know how
many people really wrote anything like swtch ().

Finger grog at FreeBSD.org for PGP public key.
See complete headers for address and phone numbers.
This message is digitally signed.  See
http://www.lemis.com/grog/email/signed-mail.php for more details.
If your Microsoft MUA reports problems, please read
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 195 bytes
Desc: not available
URL: <http://minnie.tuhs.org/pipermail/tuhs/attachments/20100930/4857efaa/attachment.sig>

More information about the TUHS mailing list